Bone repair systems

ABSTRACT

Bone treatment plate assemblies, methods of fabrication, and methods of use. Such assemblies comprise spring structures assembled to bone treatment plates. The spring structure comprises elongate bands, and springs between the bands, urging the bands against structure of the plate. Spring width is less than spring height and/or one or more protuberances extending from the band or bands cooperate with one or more detents in the plate thereby to arrest longitudinal movement of the spring structure with respect to the plate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §120 to applicationSer. No. 10/202,705 filed Jul. 24, 2002, and to Ser. No. 10/627,065filed Jul. 24, 2003 which claims priority to application Ser. No.10/202,705 filed Jul. 24, 2002 and to application Ser. No. 10/014,409filed Dec. 14, 2001; all the above of which are incorporated herein byreference in their entireties.

BACKGROUND

The present invention relates to devices for the fixation and/or supportof bones. In particular, the present invention relates to a bonetreatment plate assembly, a corresponding bone treatment plate, and aspring structure, all directed to treatment of bones of e.g. the spinalcolumn. The plate of the present invention has particular application insituations where compression or settling forces, as well as torsionaland flexing forces, of e.g. “fixed” vertebrae on a bone, treatmentplate, cause significant stressing and potential failure of the bonetreatment plate and/or plate components, or unacceptable stressing orother deleterious affect on the bones being treated.

Vertebral fixation has become a common approach to treating spinaldisorders, fractures, and the like, and for fusion of vertebrae at thetime such fixation is instituted. Namely, one or more vertebrae arefixed in position relative to one or more other vertebrae above and/orbelow the vertebrae to be fixed. Generally, a bone treatment plate,namely a spinal plate, is the device of choice used for mechanicallysupporting such vertebral fixation. A typical spinal plate includes aplate having a plurality of apertures therethrough. A plurality offasteners, i.e., bone screws, are generally positioned into and throughrespective ones of the apertures of the plate to thereby attach thespinal plate to bone, such as to two or more respective upper and lowersupporting adjacent spinal vertebrae. The screws are fastened to therespective support vertebrae to thereby attach the spinal plate to thesupport vertebrae. In general, such plate and screw assemblies can beutilized, for example, for anterior fixation of the spine for cervical,lumbar, and/or thoracic fixation.

The basis of anterior fixation or plating is to approach the spine froman anterior or anterio-lateral approach, and use the screws to solidlymount the spinal plate to the vertebrae being treated. In addition tothe application of a spinal plate, graft material may be combined withthe vertebrae, or vertebrae elements, as an assist in permanently fusingtogether adjacent vertebrae. The graft material can consist of bonegraft material obtained from bones of the recipient, or bone graftmaterial obtained from another individual.

A common problem associated with the use of such spinal bone treatmentplates is the tendency of the bone screws to “back out” or pull away orotherwise withdraw from the bone into which they are mounted. Thisproblem occurs primarily as a response to the normal torsional andbending motions of the body and spine. This is a particularly importantproblem in that, as the screws become loose and pull away or withdrawfrom the bone, the heads of the screws can rise above the surface of thespinal plate and, possibly, even work their way completely out of thebone. While this condition can cause extreme discomfort for therecipient user of the spinal plate, any substantial withdrawal of thescrews from the bone/plate can also create a number of potentiallyserious physiological problems given the significant amount of nervousand vascular structures located at or near the potential locations ofanterior spinal plate fixations.

A number of plate assembly designs have been proposed in attempts toprevent screws from pulling away or withdrawing from the bone and/or toprevent the screws from backing out or pulling away or withdrawing fromthe surface of the spinal plate. Such mechanisms used to prevent bonescrews from pulling out of bones include cams which engage and lock thescrews, and the use of expanding head screws which expand outwardly whenadequate force is applied thereto to engage the holes in the spinalplate. All of these designs have detriments, which include potential forbreakage of the screws, or which require particular precision andalignment in their application in order to work correctly. Additionally,loose components and accessories of spinal plates, which address the“backing-out” or withdrawal problem, can get dropped and/or misplacedwhile the e.g. vertebral fixation surgical procedure is taking place,prolonging and complicating the procedure which results in increasedrisk of harm to the recipient.

Yet another common phenomenon associated with the use of such spinalplates is the tendency, of the vertebrae which are being treated, tosettle after the spinal plate has been installed. Such settling addscompression forces to the above-listed forces, and raises theprobability that one or more of the bone screws will break, will backout, or pull away, or otherwise decouple, from the bone to which suchbone screw was mounted.

It is an object of the invention to provide bone treatment plateassemblies which facilitate secure bone-to-bone fixation and/or support,such as at e.g. adjacent or second adjacent vertebrae, whileaccommodating bone-to-bone settling and axial loading, as well aspost-procedural compression between the respective bones.

It is another object of the invention to provide bone treatment plateassemblies which afford substantial protection against pulling away orwithdrawal of mounting components, which pulling away or withdrawal mayresult from e.g. torsional movement, flexing movement, or stress and/ordynamic load sharing of the vertebrae, the protection thereby enhancingthe bone rebuilding process carried on routinely by the living body.

It is yet another object of the invention to provide bone treatmentplate assemblies which attenuate application of stress on the plateapparatus and on the affixing components.

It is a further object of the invention to provide bone treatment plateassemblies comprising a bone treatment plate and a spring structurehaving resiliently movable spring-like material having resilientproperties, the assemblies being so mounted and positioned as to enablebone fasteners to move past such spring-like material, withcorresponding flexing or other movement of such spring-like material,when the bone fasteners are being installed in a recipient user andwhich, in combination with the designs of the bone fasteners, preventunintentional withdrawal of the bone fasteners after installation of thebone fasteners in the recipient user.

It is still a further object of the invention to provide a springstructure, in a bone treatment plate assembly comprising a bonetreatment plate, wherein the spring structure includes resilientlymovable spring-like material having resilient properties, includingsprings, e.g. straight-line compression springs, wherein the width of agiven spring is less than the height of the respective spring.

It is still a further object of the invention to provide a spring, in abone treatment plate assembly comprising a bone treatment plate whereinthe spring structure includes resiliently movable spring-like materialhaving resilient properties, including folded or curvilinear compressionsprings wherein the width of a given spring is less than the height ofthe respective spring.

A still further object of the invention is to provide a spring structurefor use in a bone treatment plate assembly comprising a bone treatmentplate, wherein the spring structure comprises first and second opposingand longitudinally-extending bands, springs between the bands, andlocking protuberances extending from the bands and engagingcorresponding receiving detents in such plate.

It is yet a further object of the invention to provide bone treatmentplate assemblies, such as spinal plate assemblies, which can becompletely pre-assembled such that no assembly steps need be performedon the spinal plate assembly, itself, as part of the surgical procedurewhereby the spinal plate assembly is being installed in a recipient userthereof.

It is still a further object of the invention to provide bone treatmentplate assemblies wherein apparatus, in such bone treatment plateassemblies, for preventing withdrawal of bone fasteners from the bone,after installation of the bone fasteners in a recipient user, areautomatically activated, to prevent such withdrawal, as a consequence ofthe installation of suitably-configured such bone fasteners.

SUMMARY

This invention provides novel spinal plate assemblies, methods offabricating such e.g. spinal bone treatment plate assemblies, andmethods of using such plate assemblies. Such bone treatment plateassembly comprises a spring structure assembled to a bone treatmentplate. The spring structure comprises first and second elongate bands,biased against each other, by springs which extend between the plates,and resiliently urges the bands away from each other when the bands areurged toward each other by an outside force. The bands are juxtaposedproximate, and extend into, fastener-receiving-apertures in the bonetreatment plate. Widths of the springs are collectively less thanheights of the springs, whereby the ratio of spring width to springheight is less than 1/1; and/or protuberances extend from one or bothbands, and engage detents in the plate, thereby to arrest and/or preventlongitudinal movement of the spring structure relative to the plate.

In a first family of embodiments, the invention comprehends a springstructure having first and second ends, a length, a structure top and astructure bottom, and a structure height therebetween. The springstructure further comprises first and second bands each having first andsecond ends, a band top, and a band bottom associated with the structuretop and the structure bottom, the bands having respective lengths, thefirst and second bands each having an outer surface facing outwardly ofthe spring structure, and an inner surface, the inner surfaces facingeach other and facing inwardly into the structure, the first and secondbands defining a width of the spring structure between the outersurfaces; and springs spaced along the length of the spring structure,the springs extending between and connected to the bands, and havingspring lengths extending between the first and second bands, the springshaving spring tops and spring bottoms, opposing spring sides, springheights between the spring tops and the spring bottoms, spring widthsbetween the opposing spring sides, angles α being defined between thesprings and the inner surfaces of the bands, and angles β being definedbetween the band tops and the spring tops, ratio of the widths of thesprings to the heights of the springs being less than 1/1 whereby, whena squeezing force is imposed on the spring structure, squeezing thefirst and second bands toward each other, the springs deflect so as toaccommodate reduced width of the spring structure in preference todeflecting in a direction corresponding to the height, such that theresponse of the spring structure to such squeezing force is apreferential change in magnitude of angle α relative to change inmagnitude of angle β.

In preferred embodiments, when the squeezing force is imposed on thespring structure, change in magnitude of angle β is substantially zero.

In preferred embodiments, the ratio of spring width to spring height isno more than 0.8/1, more preferably about 0.15/1 to about 0.7/1, stillmore preferably about 0.2/1 to about 0.5/1, and most preferably about0.25/1 to about 0.35/1. The lower ones of the ratios typically providethe relatively greater divergence between the changes in magnitudes ofangles α and β.

In some embodiments, the springs are arranged in groups of at least twosprings, preferably at least three springs along the bands.

In some embodiments, the springs comprising (i) at least three groups ofsprings wherein each group comprises at least two springs, and whereinspacing between the springs in a group is less than spacing between thegroups, or (ii) at least 6 individual springs substantially equallyspaced from each other.

In some embodiments, the springs comprise folded springs.

In other embodiments, the springs comprise substantially straight linecompression springs.

In some embodiments, the compositions of the first and second bandsand/or the compositions of the springs comprise at least one oftitanium, titanium alloy, and stainless steel.

In preferred embodiments, the first and second bands, in combinationwith the springs, define a unitary structure derived from a singleunitary work piece.

In some embodiments, the spring structure, or elements of the springstructure such as the bands and/or the springs, comprise plasticcomposition which is safe for use in living human or animal bodies, asan implantable plastic, and wherein the spring structure has suitablestrength, rigidity, and deflection properties to block screw withdrawalin a routine implant use environment.

In preferred such embodiments, the plastic composition of the springstructure comprises one or more materials selected from the groupconsisting of polyetherimide copolymer, acetal copolymer,polyethersulfone, polyarylethersulfone, polycarbonate, ultra highmolecular weight polyethylene, polyetheretherketone, andpolyaryletherketone, and blends and mixtures of the materials.

In preferred embodiments, at least one of the bands comprises amovement-arresting protuberance extending outwardly therefrom.

In some embodiments, the bands comprise first and second protuberancesextending from the bands and being effective, in combination withcooperating detents in a cooperating structure, and wherein the springstructure is otherwise confined with respect to such other cooperatingstructure, to arrest longitudinal movement of the spring structure alongsuch other cooperating structure.

In some embodiments, the bands comprise first and second protuberancesextending from the bands at or proximate the first ends of the bands,and third and fourth protuberances extending from the bands at orproximate the second ends of the bands, the first, second, third, andfourth protuberances collectively being effective, in combination with acooperating detent in another cooperating structure, and wherein thespring structure is otherwise confined with respect to such othercooperating structure, to arrest longitudinal movement of the springstructure along such other cooperating structure.

In a second family of embodiments, the invention comprehends a bonetreatment plate assembly, comprising a bone treatment plate, the bonetreatment plate comprising a top and a bottom, and a plurality ofbone-fastener-receiving apertures, the bone treatment plate furthercomprising a thickness between the top and the bottom, a channelextending alongside respective ones of the apertures, the channel havinga collective length, and a side wall, the side wall of the channelhaving an opening therein extending into a respective one of thefastener-receiving apertures; and spring structure in the channel, thespring structure having first and second ends, a length, a structure topand a structure bottom, and a structure height therebetween, the springstructure further comprising (i) first and second bands each havingfirst and second ends, a band top, and a band bottom associated with thestructure top and the structure bottom, the bands having respectivelengths thereof, the first and second bands each having an outer surfacefacing outwardly of the spring structure, and an inner surface, theinner surfaces facing each other and facing inwardly into the springstructure, the first and second bands defining a width of the springstructure between the outer surfaces, and extending along the length ofthe channel in the bone treatment plate, and (ii)springs spaced alongthe length of the spring structure, the springs extending between andconnected to the bands, and having spring lengths extending between thefirst and second bands, the springs having spring tops and springbottoms, opposing spring sides, spring heights between the spring topsand the spring bottoms, spring widths between the opposing spring sides,angles α being defined between the springs and the inner surfaces of thebands, and angles β being defined between the band tops and the springtops, the springs urging the spring structure into engagement with theside wall of the channel, ratio of the widths of the springs to theheights of the springs being less than 1/1, whereby, when a squeezingforce is imposed on the spring structure, squeezing the first and secondbands toward each other, sufficient to assemble the spring structure tothe bone treatment plate, the springs deflect so as to accommodatereduced width of the spring structure in preference to deflecting in adirection corresponding to height, such that the response of the springstructure to the squeezing force is a preferential change in magnitudeof angle α relative to change in magnitude of angle β.

In some embodiments, when the squeezing force is imposed on the springstructure, change in magnitude of angle β is substantially zero.

In some embodiments, the first and second bands extend alongsubstantially the entirety of the length of the channel, the first andsecond bands collectively extend into and across portions of each of thebone-fastener-receiving apertures.

In some embodiments, the side wall of the channel comprises a first sidewall, the channel further comprising a second side wall, the bonetreatment plate further comprising first and second rows of thebone-fastener-receiving apertures extending along the length of the bonetreatment plate, the channel extending along the length of the bonetreatment plate, the channel further comprising a second side, first andsecond overhanging top walls of the channel extending inwardly from theside walls of the channel, the overhanging top walls being effective torestrain movement of the spring structure out of the channel through thetop of the channel, the first and second elongate bands preferably beingurged by the spring structure against the respective first and secondside walls of the channel, and thus across a portion of each respectiveaperture in the first and second rows.

In preferred embodiments, as a bone fastener is driven, the bonefastener urges the respective band to move, from a first positiontransversely of the length of the band, with corresponding flexing ofthe spring structure, from a first flexural condition, until the bonefastener moves past the band, whereupon the spring structure returns theband to a position wherein the band overlies and blocks the bonefastener and thereby inhibits withdrawal of the bone fastener past theband.

In preferred embodiments, the bands are sufficiently small incross-section, and are properly positioned over the apertures, and thespring structure is sufficiently resilient, to let a bone fastener passbelow a respective one of the bands, with transverse movement of theband, and without exceeding any flexural limit of the spring structure,such that the spring structure then resiliently returns the band to ablocking position over the bone fastener.

In some embodiments, the channel is expressed intermittently along thelength of the plate.

In some embodiments, the bone-fastener-receiving apertures are spacedalong the length of the bone treatment plate, the channel is elongateand extends along the length of the bone treatment plate, the springstructure comprises a plurality of band-spring combinations, eachcomprising ones of the bands and ones of the springs, positioned in thechannel, the band-spring combinations being disposed lengthwise of eachother, and disposed alongside respective ones of the apertures, spacersbeing positioned between respective adjacent ones of the band-springcombinations so as to inhibit substantial longitudinal movement of theband-spring combinations.

In some embodiments, the spacers are held in position in the channel byprotuberances on ones of the bands and/or the spacers, whichprotuberances cooperate with detents in the channel.

In preferred embodiments, the channel comprises a plurality of walls,including the side wall, extending at least intermittently along thelength of the channel, at least one of the bands comprising at least oneprotuberance, the walls of the channel collectively comprising at leastone cooperating detent, optionally at least first and second detents,configured and positioned to receive the at least one protuberance onthe respective at least one band, the at least one protuberance and theat least one detent thereby being effective to arrest longitudinalmovement of the spring structure along the length of the channel as thespring structure is moved along the bone treatment plate.

In preferred such embodiments, the detent arrests longitudinal movementof the spring structure when the entirety of the length of the springstructure has been received into the channel.

In some embodiments, the channel comprises a plurality of walls,including the side wall, extending along the length of the channel,first and second protuberances extending from the bands on opposingsides of the spring structure and toward respective ones of the walls ofthe channel, the walls of the channel comprising at least first andsecond detents, configured and positioned to receive the protuberances,the combination of the first and second protuberances and the first andsecond detents being effective to arrest longitudinal movement of thespring structure along the length of the channel.

In preferred embodiments, the first and second protuberances extendoutwardly from the outer surfaces of the bands.

In some embodiments, the first and second protuberances are disposed atthe first end of the spring structure.

In some embodiments, the bone treatment plate assembly further comprisesthird and fourth protuberances at the second end of the springstructure, and cooperating third and fourth detents in the walls of thechannel.

In some embodiments, at least one protuberance and at least onecooperating detent are collectively configured to arrest longitudinalmovement of the respective spring structure or band-spring combinationin either of two opposing longitudinal directions.

In some embodiments, the at least one protuberance comprises a singleprotuberance and/or the at least one detent comprises a single detent,whereby the single protuberance or single detent is configured to arrestor otherwise restrict longitudinal movement of the spring structure ineither of the two longitudinal directions possible in the channel.

In a third family of embodiments, the invention comprehends a springstructure having first and second ends, a length, a structure top and astructure bottom, and a structure height therebetween. The springstructure comprises first and second bands each having first and secondends, a band top, and a band bottom associated with the structure topand the structure bottom, the bands having respective lengths, the firstand second bands each having an outer surface facing outwardly of thespring structure, and an inner surface, the inner surfaces facing eachother and facing inwardly into the structure, the first and second bandsdefining a width of the spring structure between the outer surfaces; andsprings spaced along the length of the spring structure, the springsextending between and being connected to the bands, and having springlengths extending between the first and second bands, the springs havingspring tops and spring bottoms, opposing spring sides, spring heightsbetween the spring tops and the spring bottoms, and spring widthsbetween the opposing spring sides, the spring structure comprising atleast one protuberance extending outwardly from the outer surface of arespective one of the bands, the at least one protuberance beingeffective, in combination with cooperating at least one detent in acooperating structure, and wherein the spring structure is otherwiseconfined with respect to such other cooperating structure, to arrestlongitudinal movement of the spring structure along the othercooperating structure.

In some embodiments, the bands comprise first and second protuberancesextending from the bands at or proximate the first ends of the bands,and third and fourth protuberances extending from the bands at orproximate the second ends of the bands, the first, second, third, andfourth protuberances collectively being effective, in combination withcooperating detents in another cooperating structure, and wherein thespring structure is otherwise confined with respect to such othercooperating structure, to arrest longitudinal movement of the springstructure along the other cooperating structure.

In some embodiments, angles α are defined between the springs and theinner surfaces of the bands, and angles β are defined between the bandtops and the spring tops, and ratio of the widths of the springs to theheights of the springs is less than 1/1, whereby response of the springstructure to a squeezing force, squeezing the bands toward each other,is a preferential change in magnitude of angle α relative to change inmagnitude of angle β.

In a fourth family of embodiments, the invention comprehends a bonetreatment plate assembly, comprising a bone treatment plate, the bonetreatment plate comprising a top and a bottom, and a plurality ofbone-fastener-receiving apertures, the bone treatment plate furthercomprising a thickness between the top and the bottom, a channelextending alongside respective ones of the apertures, the channel havinga collective length, and having walls extending at least intermittentlyalong the length of the channel; and spring structure in the channel,the spring structure having first and second ends, a length, a structuretop and a structure bottom, and a structure height therebetween, thespring structure further comprising (i) first and second bands eachhaving first and second ends, a band top, and a band bottom associatedwith the structure top and the structure bottom, the bands havingrespective lengths thereof, the first and second bands each having anouter surface facing outwardly of the spring structure, and an innersurface, the inner surfaces facing each other and facing inwardly intothe spring structure, the first and second bands defining a width of thespring structure between the outer surfaces, and extending along thelength of the channel in the bone treatment plate, and (ii)springsspaced along the length of the spring structure, the springs extendingbetween, and being connected to the bands, and having spring lengthsextending between the first and second bands, the springs having springtops and spring bottoms, opposing spring sides, spring heights betweenthe spring tops and the spring bottoms, and spring widths between theopposing spring sides, at least one of the bands comprising aprotuberance, the walls of the channel collectively comprising at leastone detent configured and positioned to receive the protuberance on therespective band, the combination of the at least one protuberance andthe at least one detent being effective to arrest longitudinal movementof the spring structure along the length of the channel as the springstructure is advanced along the channel.

In some embodiments, the bands comprise first and second protuberancesextending from the bands at or proximate the first ends of the bands,and third and fourth protuberances extending from the bands at orproximate the second ends of the bands, the first, second, third, andfourth protuberances collectively being effective, in combination withthe walls of the plate, and wherein the spring structure is otherwiseconfined with respect to the channel, to arrest longitudinal movement ofthe spring structure with respect to the channel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a pictorial view of a first embodiment of bone treatmentplate assemblies of the invention, including a bone treatment plate.

FIG. 2 shows a top view of the bone treatment plate assembly illustratedin FIG. 1.

FIG. 3 shows a bottom view of the bone treatment plate assemblyillustrated in FIG. 1.

FIG. 4 shows a side view of the bone treatment plate assemblyillustrated in FIG. 1.

FIG. 5 shows a cross-section of the bone treatment plate illustrated inFIGS. 1-4, and is taken at 5-5 of FIG. 4.

FIG. 6 shows a cross-section of the bone treatment plate assembly ofFIGS. 1-4 and is taken at 6-6 of FIG. 4.

FIG. 7A shows a top view of a first embodiment of spring structureswhich are incorporated into bone treatment plate assemblies of theinvention, and wherein the springs are shown in groups of three.

FIG. 7B shows a top view of a second embodiment of spring structureswhich are incorporated into bone treatment plate assemblies of theinvention, and wherein the springs are generally evenly spaced along thelength of the spring structure.

FIG. 7C shows a top view of a third embodiment of spring structureswhich are incorporated into bone treatment plate assemblies of theinvention, wherein the springs are folded leaf constructs which aregenerally evenly spaced along the length of the spring structure.

FIG. 8 shows a side elevation of the spring structure of FIG. 7A.

FIG. 9A shows a top view of an enlarged portion of an end section of thebone treatment plate of FIG. 2, with parts cut away.

FIG. 9B shows a top view as in FIG. 9A, with the spring structure ofFIG. 7A assembled into the plate channel.

FIG. 10 is a cross-section of a leaf element of a spring of FIG. 7A,illustrating the ratio of width to height of the spring.

FIG. 10A is a cross-section of the spring structure of FIG. 7B, taken at10A-10A of FIG. 7B.

FIG. 11A is a cross-section of a bone treatment plate assembly as inFIGS. 1-4, showing the band deflected by the passing of the head of abone screw in contact with the band.

FIG. 11B is a cross-section as in FIG. 11A wherein the head of the bonescrew has passed the bottom of the band thus to enable the band torevert toward or to its undeflected and blocking position over the headof the bone screw.

FIG. 12 shows a top view of a segmented spring structure combinationemploying spacers between a multiplicity of relatively shorter-lengthspring structures.

FIG. 13 is a top view of a bone treatment plate assembly of theinvention employing the segmented spring structure combination of FIG.12.

The invention is not limited in its application to the details ofconstruction or the arrangement of the components set forth in thefollowing description or illustrated in the drawings. The invention iscapable of other embodiments or of being practiced or carried out inother various ways. Also, it is to be understood that the terminologyand phraseology employed herein is for purpose of description andillustration and should not be regarded as limiting. Like referencenumerals are used to indicate like components.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Referring now to the embodiments represented by FIGS. 1-6 and 7A, a bonetreatment plate assembly 10 of the invention includes a spinal plate 12,which functions as a bone treatment plate, supporting cooperating bonestructure in a recipient user. Assembly 10 further includes a springstructure generally represented by 14 in FIGS. 1 and 7A.

Spinal plate 12 has a top surface 18, a bottom surface 20 adapted to bepositioned adjacent bone structure of a recipient user of the spinalplate assembly, and a plurality of bone-fastener-receiving apertures 22which receive bone fasteners such as bone screws 24. Apertures 22 arearranged in first and second rows of such apertures, along the length ofthe spinal plate.

Top surface 18 of the spinal plate defines a channel 26 extending alongthe length of the spinal plate. Channel 26 has a bottom wall 28,opposing side walls 30, and has openings 32 extending out the respectiveends of spinal plate 12, best illustrated in FIGS. 1, 9A, and 9B.Channel 26 further has overhanging top walls 34 extending inwardly fromthe side walls of the channel and spaced from each other and from thebottom wall, thereby leaving an opening 35 in the top of the channelbetween the overhanging top walls, and extending along the length of thechannel. Opening 35 can be eliminated if desired so long as adequatestructure is employed to hold spring structure 14 in proper position inchannel 26. The cross-sectional area 37 of the open cross-section of thechannel, as defined between side walls 30 and top and bottom walls 28and 34, is preferably generally constant along substantially the fulllength of plate 12. Side walls 30 of the channel are specificallylocated and configured so as to open into the sides of, and extend alongand inwardly of the sides of, apertures 22. In general, imaginaryextensions of side walls 30 project across apertures 22 at locationsdisplaced inwardly of the aperture side walls by distances “D” of about1 mm.

FIG. 7A illustrates a preferred embodiment of spring structure 14 whichis incorporated into the assembly illustrated in FIG. 1. As seen in FIG.7A, spring structure 14 includes first and second elongate bands 36A,36B extending parallel to each other and in a common plane or in acommon curvilinear surface. Bands 36A, 36B are connected to each otherby three groups 38A, 38B, 38C. Thus, group 38A includes springs 38A1,38A2, 38A3. Group 38B includes springs 38B1, 38B2, and 38B3. Group 38Cincludes springs 38C1, 38C2, and 38C3. In the embodiment illustrated inFIG. 7A, springs 38 are substantially straight line compression springsconnected to bands 36A, 36B at generally straight line acute angles α,as seen in the top view, of about 10 degrees to about 30 degrees, e.g.about 15 degrees to about 20 degrees, to the respective bands. Referringto FIG. 10A, the top of each spring 38A, 38B, 38C also forms an angle βwith the tops of respective bands 36A, 36B.

Groups 38A, 38B, 38C of springs represent only one of a wide variety ofoptions for extending compression springs between the bands for biasingthe bands against each other and thus for urging the bands away fromeach other. While 3 groups of springs are shown, any number of springscan be used in a wide array of possible groupings, with suitableadjustment of the force exerted by each spring. Correspondingly, agreater, or lesser, number of groups of springs can be employed.

As used herein, a group of springs is a collection of adjacent springs,namely two or more springs, which are substantially more closely spacedwith respect to each other than to other next adjacent springs.

The spring structure, including bands 36 and the individual springsgenerally designated with the digits 38, is preferably fabricated from asingle unitary generally planar work piece, of generally uniformthickness “H”. In such instance, the thickness or height “H” of springstructure 14 also is the height “H” of the respective springs 38. Theheights of the springs can be greater than, or less than, the heights ofthe bands, but such is not normally the case.

Spring structure 14 is preferably fabricated from a single sheet ofmaterial. Preferred method of fabricating the spring structure is to uselaser cutting apparatus to cut away waste material so as to leave bands36 and springs 38 as suggested at e.g. FIGS. 7A, 7B, and 7C.

In preferred expressions of this invention, the width “W” of springelements 38, as illustrated in FIGS. 7A and 10, are less, preferablysubstantially less, than the heights “H” of the respective springelements. Stated another way, the average width “W” is less than theaverage height “H”. In preferred embodiments, the width “W” of eachspring element is less than the height “H” of the respective springelement. Thus, the ratios of width “W” to height “H” are preferably lessthan 1/1. In typical embodiments, and as illustrated in FIG. 10, the W/Hratio, for a given spring is about 0.15/1 to about 0.7/1, whereas morepreferred embodiments employ W/H ratios of about 0.2/1 to about 0.5/1.Most preferred embodiments employ W/H ratios of about 0.25/1 to about0.35/1. Accordingly, the bending resistance of a given spring in thewidth direction “W”, e.g. in the rest plane of the spring structure,e.g. as the bands are squeezed toward each other, is less than thebending resistance of that spring in the height direction “H”, namely adirection which would take the springs out of the plane or planes ofband or bands 36.

As used herein, “plane” as applied to the spring structure, especiallyto bands 36, includes moderately curved surfaces such as thoseillustrated in FIGS. 1 and 4. However, the materials of both bands 36and springs 38 are resilient whereby a truly flat planar structure canreadily conform to the modest curvature of a plate 12 configured withthe modest curvature of the plates of FIGS. 1 and 4.

Given the moderate rest magnitude of angle α, at least a substantialvector of the width “W” of the spring element is aligned with the width“W1” of the spring structure. Accordingly, given the relative bendingresistances in the “W” and “H” directions, when a force is exertedagainst the spring structure, generally along the direction of width“W1”, thus to urge bands 36A, 36B toward each other, the springstructure tends to respond by collapsing inwardly thereby to reducewidth “W1” of the spring structure, thereby reducing the magnitude ofangle α in preference to changing the magnitude of angle β. Whilesuitably sensitive instrumentation can likely measure some deflection inangle β, such change in angle β preferably approximates zero. Meantime,change in angle α is desired to be substantial. Thus, the ratio ofchange in angle α to change in angle β, when a squeezing force, which isnot a collapsing force, is exerted on bands 36A, 36B, is preferablysubstantially greater than 1/1 and can approach infinity. As the ratioof width “W” of the spring to height of the spring is increased, theratio of such change in angle α to change in angle β decreases. Such α/βratio is preferably at least 3/1, more preferably at least 10/1.Correspondingly, any width/height ratio of the spring of less than 1/1is an improvement over known art, and thus within the scope of theinvention. Thus, a width to height ratio of e.g. 0.8/1 is within thescope of the invention. Indeed, any spring 38 which exhibits a width toheight ratio of less than 1/1, and which shows a preference for changeof angle α in preference to angle β is within the scope of the invention

By contrast, since resistance to bending in the “H” direction isrelatively greater than resistance to bending in the “W” direction,namely bending the spring in the relatively larger “H” dimension of thespring is more difficult than bending the spring in the relativelysmaller “W” dimension of the spring, the bands remain in a generallycommon plane while the bands move into a converging/divergingrelationship with respect to each other when a compressive/squeezingforce is applied to the outer edges of the spring structure.

In the illustrated embodiments, all the springs have the same widths“W”. In other embodiments, not shown, widths of the springs varies fromspring to spring; while the average W/H ratio is substantially less than1/1.

FIG. 7A illustrates three springs in each group of springs. A lesser orgreater number of springs can be used as desired in each group. Indeed,the number of springs in a respective spring structure can also beselected as desired, and can be more or less than the numbers of springsillustrated in the drawings. For example, FIG. 7A shows 9 springswhereas FIGS. 7B and 7C show 11 springs.

Where groupings are used as illustrated in FIG. 7A, it is preferred thatthe collective total of the widths “W” of a given group of springs isnot substantially greater than the height “H” of the spring structure.The total of the widths of the springs determines the overall resistanceto compression/squeezing force. However, where a group is looselydefined in terms of the springs being spread out over a relativelylarger length of the spring structure, for example all springs evenlyspaced from each other as shown in FIGS. 7B and 7C, adjustment must bemade to the foregoing statement to account for the spacing of thesprings.

Where the collective total width “W” of a grouped set of springs is onthe upper side of the W/H range, resistance to squeezing the springstructure, as affected by a given such spring, e.g. for assembly intothe plate, is relatively greater. Accordingly, in such case, anddepending on the material from which the springs are fabricated, in someinstances, a smaller number of springs can be used for each springgroup.

In the alternative, whereas FIG. 7A shows three groups of springs, agreater number of groups can be employed by using a smaller number ofsprings in each of the respective groups or by reducing e.g. the averagespring width “W”. The number of springs can be the same for all groups,or can vary as desired, from group to group. As an ultimate expressionof the number of groups, each group can include only a single spring asillustrated in FIGS. 7B and 7C, wherein the springs are more or lessuniformly spaced from each other.

The width “W1” of spring structure 14 between the outer walls 46 ofbands 36A, 36B is greater at rest than the width “W2” of channel 26between side walls 30. Spring structure 14 is inserted longitudinallyinto channel 26 by squeezing the spring structure together at the widthdimension thereof, preferably at an end of the spring structure,sufficient to temporarily reduce the width “W1” of the spring structureat the respective end to a width less than width “W2” of channel 26; andby inserting the reduced-width squeezed end of the spring structure intothe end opening 32 at the end of channel 26. As the spring structure issqueezed, the squeezing is progressively resisted by the resilience ofthe compression springs, e.g. springs 38A or 38C, using the FIG. 7Astructure, between the bands. The spring or springs closest to the endbeing squeezed together is typically most affected, and is thereforemost effective in resisting such squeezing, thereby setting up aresilient force urging restitution of the compressive squeezing force,and thus urging the outer walls 46 of the spring structure intoengagement with side walls 30 of the channel as the spring structure isinserted longitudinally into channel 26. As the insertion of the springstructure progresses into channel 26, the respective compression springs38 become progressively squeezed as the springs enter channel 26, eachpreferably developing a resilient outwardly-directed force urging theouter walls 46 of the bands into engagement with side walls 30 of thechannel.

Since the side walls of the channel open into apertures 22, bands 36A,36B extend across the respective apertures 22 as the spring structure isinserted into channel 26. The length of spring structure 14 asillustrated corresponds substantially with the length of channel 26 suchthat the entirety of the length of the spring structure is receivedwithin channel 26 in the illustrated embodiments, and wherein the springstructure extends substantially the full length of channel 26. Where asingle spring structure is used, the length of the spring structureshould be at least great enough that bands 36A, 36B extend across eachof the apertures 22 in each row of apertures.

In the alternative, channel 26 can be expressed intermittently. Asillustrated in FIGS. 12 and 13, intermittent expression of the channelcan be effected by placing spacers 50 in the channel at spacedlocations, between respective fore-shortened expressions of the springstructure. In an embodiment not shown, channel 26, itself, isintermittent, whereby the space shown occupied by spacers 50 in FIGS.12, 13 is occupied, in the plate assembly, by material forming part ofthe structure of plate 12. Thus, channel 26 in such embodiments isexpressed as a series of longitudinally spaced, and relatively shorterchannels. Length of a given channel is sufficient to hold a spring orspring structure which extends into a respective adjacent aperture 22.

The intensity of resistance of spring structure 14 to compressive force,and intensity of resilient urging of bands 36 against the sides ofchannel 26, are influenced by the number and distribution of the springsalong the length of the spring structure as well as by the selection ofthe material from which the spring structure is fabricated. Theintensity of the spring effect, e.g. the collective spring constant ofthe corresponding spring structure, when a squeezing force is applied tobands 36A, 36B, is also affected by the collective widths “W” of therespective springs.

Each spring 38, in general, can have a constant height “H” and aconstant width “W” along the length of the given spring; or an effectiveheight “H” and an effective width “W”. In some embodiments, width “W” ofa spring 38 has a modest taper of e.g. about 5 degrees such that springwidth “W” is less adjacent the respective bands than toward themid-point of the length of the spring, whereby bending of the spring isrelatively more concentrated adjacent bands 36. Typically, the springsare evenly spaced along the length of the spring structure, or springgroups are evenly spaced along the length of the spring structure.

Typically, all, or nearly all, of the springs in a given springstructure have a common cross-section and a common end-to-end line ofprogression. A common line of progression is a straight line, asillustrated in FIGS. 7A, 7B. Another line of progression is a foldedback, or folded spring, or “V”-shaped spring, all being alternativenomenclatures for the structure illustrated in FIG. 7C. Still another,but not limiting, type of line of progression, not shown, is acurvilinear structure. In any event, the W/H ratio is preferably withinthe above-noted ranges, thereby to facilitate maintaining bands 36A, 36Bin a common plane as spring structure 14 is compressed and assembledinto plate 12 at channel 26. Width and/or height can, of course, bevaried along the line of progression whereupon the functionallyequivalent constant width and/or, constant height, in terms ofdeflection, is used to calculate the W/H ratio.

Referring to especially FIGS. 7A-7C and 9A-9B, protuberances 40 extendoutwardly from outer walls 46 on opposing sides of the spring structure14. In the embodiments illustrated, two protuberances are located ateach end of the spring structure. Side walls 30 have detents 42 whichcooperate with protuberances 40 to arrest/stop longitudinal movement ofside structure 14 along channel 26.

In assembling the spring structure to the plate, an end of the springstructure is squeezed together e.g. to reduce width “W1” such that thewidth of the spring structure across the protuberances on the respectiveend 32 of the channel is no greater than the width of the channel atthat end of the plate. With the width “W1” so reduced, the springstructure is then inserted longitudinally into channel 26 and pushedalong the length of the channel. As the spring structure is pushedlongitudinally into the channel, the progression of groups 38 along thelength of the spring structure are progressively squeezed by the channelside walls as the respective springs enter channel 26; and the springscorrespondingly urge the outer walls 46 of the bands 36 toward outerside walls 30 of the channel, and the protuberances at the leading endslide along and against side walls 30 of the channel. Thus, springs 38push the leading protuberances into sliding engagement with side walls30 at least by the time the full length of the spring structure isreceived into channel 26.

By the time all of the springs are within channel 26, all of thecorresponding compression springs are to some degree compressed wherebybands 36A, 36B are urged against side walls 30 along all, orsubstantially all, of the length of the channel. As the leading end ofthe spring structure reaches the distal end of the plate, and withsprings 38 at the leading end of the spring structure exerting outwardlydirected forces, urging bands 36A, 36B away from each other,protuberances 40 at the distal end of the channel are effectively pushedinto the detents 42 which are located at the distal end of the channel.

At about the same time, the protuberances at the proximal end of thechannel come into engagement with the detents 42 at the proximal end ofthe channel. The engagement between the protuberances and the detents atthe proximal end of the channel arrest the ongoing longitudinal movementof the spring structure so as to stop forward, engaging movement of thespring structure. Meantime, the protuberances and detents at the leadingend of the spring structure and plate prevent backward, disengagingmovement of the spring structure. With the protuberances of the springstructure so engaged with detents at both ends of the plate, the springstructure is held firmly in place in channel 26. Protuberances 40 anddetents 42 prevent longitudinal movement of the spring structure. Bottomwall 28 of the channel prevents downward movement of the springstructure. Top wall 34 of the channel prevents upward movement of thespring structure.

Considering that the protuberances at each end of the spring structureprevent longitudinal movement of the spring structure in only onedirection, a single set/pair of two-way protuberances 402 can be locatedaway from the ends of the spring structure, for example toward themiddle of the length of the spring structure, as indicated in dashedoutline in FIG. 7B. Detents 42 are positioned correspondingly along thelengths of side walls 30 of the channel. Where protuberances 402 arepositioned away from the ends of the spring structure, the detents canbe structured to provide interfering, arresting surfaces for coactingwith corresponding surfaces of the protuberances such that eachcombination of detent and protuberance is effective to prevent movementin either of the longitudinal directions, e.g. two-way movement, alongthe length of channel 26. Where the protuberance/decent surfaces aresuitably designed, and where springs 38 exert sufficient resilientforce, a single two-way protuberance 402, acting with a single two-waydetent, away from the ends of the channel, can be effective to arrestmovement of the spring structure in two, namely both, longitudinaldirections. Indeed, so long as the detent and protuberance are suitablyconfigured to arrest movement in both longitudinal directions, theprotuberance can be located anywhere along the length of the springstructure 14, including at the ends of the spring structure, and thedetent can be correspondingly located anywhere along the length of thechannel, even at or proximate the end of the channel, so long as thedetent is suitably restrictive, with respect to the correspondingprotuberance, to retain the spring structure in the channel.

In view of protuberances 40 and cooperating detents 42, along withchannel 26, including side walls 30 and overhanging top walls 34, springstructure 14, including bands 36A, 36B, is effectively confined inchannel 26. The spring structure is effectively prevented from movinglongitudinally by the combination of protuberances 40 and detents 42.The spring structure is effectively prevented from moving laterally byside walls 30 of the channel. The spring structure is effectivelyprevented from moving vertically by bottom wall 28 and overhanging topwalls 34. Thus, once the spring structure is inserted into the channel,and protuberances 40 are engaged with detents 42, the spring structureis effectively locked into position in channel 26. In such position,bands 36A, 36B extend across portions of the respective apertures 22 asillustrated in e.g. FIGS. 1-3.

As shown in the various drawings, springs 38 extend between therespective bands 36A, 36B, and thus bias the bands with respect to eachother. Thus, e.g. when squeezing force is applied to the springstructure to reduce the overall width of the spring structure thereby toenable the spring structure to be inserted into channel 26, springs 38are effectively biasing the bands against each other, such that a forceexerted against a first one of the bands, and directed toward the otherof the bands, is transferred at least in part to the other band, wherebythe physical properties of the bands interact with each other when suchforce is applied.

Thus, with the spring structure fully inserted into channel 26, springs38 position bands 36 solidly against the side walls of the channel atlocations where the bands are not passing through apertures 22. With thebands solidly against the side walls of the channel, theoutwardly-disposed walls 46 of the bands are in surface-to-surfacecontact with side walls 30 of the channel. The outwardly-disposed walls46 of the bands, the spring-loading of the bands, the respective rows ofapertures 22, overhanging top walls 34, protuberances 40, detents 42,and springs 38 are thus all correspondingly sized, arranged andconfigured with respect to each other such that bands 36 are trappedbetween the side walls, the channel bottom or elements of a channelbottom, the overhanging top walls, and the springs such that the bands,without external forces applied, extend along a path whereinoutwardly-disposed walls 46 of the bands extend alongside, and insurface-to-surface engagement with, side walls 30 of the channel. Sinceimaginary extensions of the side walls of the channel are displacedinwardly, into the apertures, of the aperture side walls by about 1 mm,the outwardly-disposed side walls of the bands also are displacedinwardly of the aperture side walls by a distance “D” of about 1 mm, andthus extend across corresponding portions of the projectedcross-sections of the respective apertures.

FIG. 6 shows a cross-section of the spinal plate assembly of FIGS. 1-4at an aperture 22. Thus, FIG. 6 shows bands 36A, 36B extending intoapertures 22, as well as showing a spring 38B biasing the bands intosuch position.

FIG. 8 shows a side view of the spring structure, illustrating thepreferred uniform height “H” of the spring structure along the length ofthe spring structure.

FIGS. 11A and 11B illustrate the process by which a band 36 is flexed ordeflected, or otherwise caused to move in treatment plate assembly 10,when a bone screw 24 passes the band. FIGS. 11A and 11B furtherillustrate the interference in a withdrawal path of the screw, providedby the band after the head of the screw has been driven past the bandand the band has returned to the undeflected or less deflectedcondition.

Referring to FIG. 11A, as a bone screw is advanced through an aperture22, the spring biasing of the band is effective, automatically and as aconsequence of driving the bone screw through the respective apertureand into bone structure of a recipient user, to respond to side forceapplied by an interfering element 47 such as the outer portion of thehead of the bone screw by resiliently moving transversely of the lengthof the band, and in a direction away from the interfering element, andby the band resiliently returning to a position over the interferingelement after the interfering element passes the band. After returningover the interfering element, the position of the band over theinterfering element is effective to inhibit withdrawal of the bone screwpast the band and out of the bone treatment plate assembly.

Looking specifically at FIG. 11A, as the bottom surface (e.g.interfering element) of the outer portions of the head of the bone screwengages the top outer corner of the band, the beveled or conical bottomsurface of the screw head urges the band out of interfering alignmentunder the screw head. Once the screw head, as an interfering element ofthe screw, has moved past the band, the band automatically returns to aninterfering, blocking position over the outer edge of the screw head asshown in FIG. 11B. Such interfering, blocking position over the screwhead is effective to interfere with, typically to block, withdrawal ofthat screw past that band. Thus, the band serves as a safety devicepreventing withdrawal of the bone screw from the bone, and from the bonetreatment plate assembly.

FIGS. 12 and 13 illustrate a further family of embodiments of bonetreatment plate assemblies of the invention. In the embodiments of FIGS.12 and 13, plate 12 is substantially as shown and described in theprevious embodiments. As noted hereinabove, spring structure 14 is shownas a plurality of shortened band-spring combinations 48, with spacers 50disposed between the respective band-spring combinations, the endcombinations 48 embodying protuberances 40, which are received intwo-way detents in channel 26. Thus, spring structure 14 in FIGS. 12 and13 is expressed as intermittent placement of the band-springcombinations along the length of the plate, whereby channel 26 iseffectively intermittent, with spacers 50 acting as barriers between theintermittent expressions of the channel.

In a family of embodiments (not shown), channel 26 can be intermittent,namely expressed intermittently, and exist adjacent only e.g. some orall of apertures 22. In such embodiments, bands 36A, 36B are held inchannel elements which extend e.g. downwardly from top surface 18 ofplate 12, and which channel elements thus define the band paths. Springs38 are employed as desired, such as in FIG. 12. Protuberances 40 are notneeded because end walls of the intermittent expressions of the channelsprevent longitudinal movement of the bands, whereby the retainingfunctions of the protuberances and detents are typically provided bymaterial of the plate. However, in such instances, suitable expressionsof top walls 34 are included in each expression of the channel both toaccommodate entry of the spring structure through the top of thechannel, and to prevent inadvertent release of the spring structurethrough the top of the channel.

FIGS. 12 and 13 illustrate a plurality of band-spring combinationstructures positioned in the channel, which can also be considered asintermittent expressions of a channel between spacers 50, and disposedalongside the respective pairs of apertures, with spacers 50 positionedbetween respective adjacent band-spring combinations so as to inhibitsubstantial longitudinal movement of the band-spring combinations, andto provide end surfaces, at the ends of the spacers, against which thesprings can flex inwardly as a bone screw is driven past the respectiveband. As shown, each band-spring combination includes a pair of bands 36on opposing sides of the combination element, and first and second2-direction folded leaf springs 38 at opposing ends of the combinationelement. In assembly 10, each band-spring combination is sufficientlylong to extend along substantially the full length of an adjacentaperture 22 and to engage the side walls 30 at each end of therespective aperture.

FIGS. 12 and 13 show a separate band-spring combination 48 fordeployment adjacent each pair of apertures 22. As desired, fewer suchband-spring combinations can be used wherein at least one suchband-spring combination can extend across two or more such pairs ofapertures.

Since bone treatment plate assemblies of the invention are to be usedwithin living bodies, all materials used in the bone treatment plateassemblies must be compatible with, and safe for use inside, the livingbody. In that regard, preferred material for bone treatment plate 12,spring structure 14, 48 and springs 38, is titanium, or titanium alloy,for example titanium-aluminum alloy. A specific titanium aluminum alloyreferred to in ASTM F-136 is (Ti 6AL-4V). Other titanium alloys,compatible for use in the living body, are contemplated. Preferredmaterials for bands 36 have a desired level of resilient flexuralcapacity. Safety is typically controlled by composition and structure.In this analysis, exemplary structure is shown in the drawings herein;and composition is the variable being analyzed for safety.

Plate 12 has a length sufficiently long to span at least two vertebrae,and width and thickness sufficiently great to provide resistence tobending and torsion forces. Accordingly, where plate 12 is composed ofone of the above referred-to materials, typical dimensions are asfollows. Typical length is at least 20 mm, up to as great as about 120mm or more. Width is typically about 15 mm to about 20 mm. Nominalthickness is typically about 2 mm to about 3.5 mm. The bottom of channel26 is typically about 0.7 mm to about 1.5 mm from the top surface of theplate. Typical nominal depth of channel 26, from the bottom of thechannel to any overhanging top wall, is about 0.5 mm. Such dimensionsare, of course, exemplary only and not limiting and, given the aboveexemplary dimensions, those skilled in the art can vary such dimensionsaccording to specific structure of respective plates and plateassemblies.

In addition, the plate assembly materials must perform the requiredphysical functions of flexing enough, when properly positioned overapertures 22, to let the bone screws pass below the bands withoutexceeding the flexural limits, collectively, of the band materials orthe springs, and must return to blocking positions over the screws orother control structure after passage of the bone screws. Such flexuralproperties are based on physical properties inherent in the materialcompositions, in combination with the physical cross-sections of thebands and springs.

The resilient properties can be provided by bands 36, by springs 38, orby a combination of bands 36 and springs 38. Thus, bands 36 can besubstantially non-flexible and substantially all the resilience can beprovided by the flexibility of springs 38. In the alternative thestructures shown as springs 38 can be substantially non-flexible, namelycan perform a rigid blocking function once installed in channel 26,whereby most, or substantially all, of the resilience is provided bybands 36. Typically, the ability of bands 36 to move, in response toadvance of a bone screw, is provided in part by each the band and atleast one spring, preferably all of the springs, working cooperativelytogether.

In preferred embodiments, but not all embodiments, bands 36 and springs38 are fabricated from a single piece of material whereby the inherentphysical properties of the bands and the springs are the same.Typically, the resilience in such combination is provided by thecombination of springs 38 and bands 36. The resiliences provided by therespective bands and springs in such combination are neverthelessdependent on the respective widths and thicknesses of the bands andsprings, as well as on the angles expressed between the springs and thebands at any given time. Thus, considering the element widths suggestedin FIG. 10A, assuming common material, one would expect substantiallyall the resilient bending to take place in springs 38, at least relativeto bands 36.

The greater the included acute angle α between a band and a respectivespring 38, the relatively greater the spring constant/degree ofresistance which the spring can exert against a force squeezing thebands 36A, 36B toward each other. The smaller the included angle α, therelatively less the spring constant/degree of resistance. Thus, byvarying angle α and/or spring width “W” and/or band width “W3”, thesprings and bands can be engineered for a wide range of desired degreesof resilient restoration force to be provided by the respective bandsand springs.

In some embodiments, such as where plate 12 has only a single row ofapertures 22, width “W3” of band 36B can be greater than width “W3” ofband 36A. In such instance, typically band 36B extends across apertures22 and band 36A serves as a connector to connect springs 38 together.

Since the spring structure in such embodiments is thus asymmetric withrespect to widths “W3” of bands 36, it is desirable to fabricate springstructure 14 so as to assure proper orientation of the spring structurein channel 26. To that end, detents 42 can be fabricated only in theside wall 30 which extends along the apertures 22; and protuberances 40can be fabricated only on the wider one of the bands 36 which is to bejuxtaposed against and over apertures 22, whereby the other band isdevoid of protuberances.

In the alternative, other structural and/or dimensional relationshipscan be employed to assure proper orientation of spring structure 14 inchannel 26.

Certain materials which are not generally considered as havingresilient, spring-like properties can, when fabricated into sufficientlysmall cross-sections, perform the desired resiliently flexural springfunction of the springs or the bands. For example and withoutlimitation, bands 36 can employ titanium compositions, titanium alloycompositions such as titanium-aluminum alloy compositions such as theabove-mentioned specific alloy, or other titanium alloys, or stainlesssteel compositions which, in sufficiently small cross-section, canexhibit the desired resilient spring-like properties. Other materialscan be used as bands 36 and springs 38 so long as such materials satisfythe above safety and performance requirements.

Any of the plastic materials known to be safe for use in living human oranimal bodies, as applies, as implantable plastics, and which havesuitable hardness, rigidity, and resilience, can be employed forfabricating bands 36 and springs 38. As with the metals, such materialsmust be both bio-stable and bio-compatible.

As such plastics, there can be mentioned, for example and withoutlimitation,

-   -   polyetherimide copolymer such as ULTEM®,    -   acetal copolymer,    -   polyethersulfone, also known as polyarylsulfone, such as RADEL        A®,    -   polyarylethersulfone such as RADEL R®,    -   polycarbonate,    -   ultra high molecular weight polyethylene,    -   polyetheretherketone, also known as PEEK, available from        Boedecker Plastics, Inc. Shiner, Tex.,    -   polyaryletherketone, also known as PEEK-OPTIMA®.

Such materials can be filled or unfilled, and can employ the usualadditives, including processing aids, so long as the resultantcomposition is suitable as an implantable plastic for use in a living,e.g. human body.

As a result of the structures of apertures 22, channel side walls 30,and spring structure 14, along with proper positioning of protuberances40 in detents 42, when a bone screw, which properly fits an aperture 22,is driven through the aperture 22, the head of the bone screw impactsthe respective band 36 as shown in FIG. 11A, and forces the band in awidth-wise transverse direction away from the center of the aperture inorder that the head of the bone screw can pass the band. Since the bandis readily and resiliently moved, against resistance of springs 38, andsince the bone screw is already embedded in bone material of therecipient user by the time the screw head reaches the band, the bandmoves in response to the urging of the head of the bone screw, as shownin FIG. 11A. When the head of the bone screw passes below the bottom ofthe band, the band is no longer being held in the moved position, andtherefore resiliently returns toward the position occupied prior tobeing moved, thereby setting up a potential interference between theband and the screw, of more or less about 1 mm, which interference isimplemented if and when the screw begins to back out of, or withdrawfrom, the spinal plate.

The invention contemplates that bands 36 can be arranged in other than aresting and straight condition when not being forced sideways by headsof bone screws. Thus, the bands can be under a degree of constantstress, e.g. pre-stressed condition, wherein the level of stress changesas the head of the screw passes, and then reverts to the previous levelof stress, or some other related stress, after the screw head passes. Ingeneral, springs 38, even without stress from a bone screw, typicallyexert a relatively modest degree of force urging bands 36 against theside walls 30 of channel 26.

Bands 36 can be arranged in a non-straight, e.g. curvilinear or anglede.g. folded, configuration when not being moved by a screw head or otherinterfering element, and can still move with respect to the bone screwas the bone screw is driven past the band.

Likewise, channel 26 can be intermittent, and can exist only adjacentapertures 22. FIGS. 12 and 13 illustrate an effectively intermittent useof spring structure 14, effectively defining spaced channel pockets,wherein spacers 50 obviate spring structure 14 extending the full lengthof plate 12, and wherein each band-spring combination 48 structure 14operates within a fabricated individual channel pocket in the plate.Each band-spring combination also embodies its own spring restorationproperties. As suggested by FIG. 13, where a band-spring combination isconfined within such a pocket, having both side walls and end walls, noprotuberance 40 or detent 42 need be employed at the band-springcombination. Namely, side walls 30, and end walls, of the pocketsuitably retain the band-spring combination from longitudinal andtransverse movement with respect to the plate and pocket, and suitabletop wall 34 and/or bottom wall 28 structure in the channel preventupward and downward movement of the spring structure with respect to thechannel.

In the alternative, protuberances 40 and detents 42 can be used withsuch intermittent structure as desired. For example, where protuberances40 are employed on each band-spring combination, albeit of relativelyshorter length, in combination with respectively located detents tocooperate with the protuberances on each band-spring combination, therelatively shorter band-spring combinations can be employed without useof intervening spacers 50.

If desired, some interfering element other than the head of the screwcan be used to activate and release the band. For example, aninterfering element (not shown) can be designed into the screw below thescrew head, above the screw head, or otherwise, for the purpose ofactivating movement and release of the band.

Whatever the positions of the bands, whatever the interfering element onthe screw, which interfaces with the band, once the band is releasedfrom the movement caused by the respective interfering element, and theband thus returns to the position which it occupied prior to having beenmoved, the band is positioned above, over, and in an interfering andblocking position with respect to, a path which some portion of thescrew must traverse in order to withdraw from the spinal plate assembly.Referring to FIG. 11B wherein the head of the screw has passed below thebottom of the band, and wherein the band has thus returned toward or tothe pre-stressed position, the band is seen to overlie a portion of thesurface of the head of the screw, such that if the screw begins towithdraw e.g. away from the plate, the head of the screw impacts thebottom of the band. As withdrawal of the screw progresses such that thescrew reaches the bottom of the band, the band, being supported byoverhanging top walls 34, or other top wall-type structure, prevents thescrew from further withdrawing from the plate.

As seen in FIG. 11A, when the screw is driven through the plate, e.g.and into bone material of a recipient user of the bone treatment plateassembly, the force applied by the upwardly-extending angular bottomsurface of the screw automatically pushes the band aside as the head ofthe screw pushes against and passes the band. Once the head of the screwpasses the band, the band is automatically restored toward or to theunmoved position over the head of the screw, illustrated in FIG. 11B.Thus, in bone treatment plate assemblies of the invention, driving thebone screw, and thereby mounting the bone treatment plate assembly inthe body of a recipient user thereof, automatically moves, optionallyflexes, the band, as a blocking member, out of the way of insertion ofthe bone screw, and then the blocking member/band automatically moves toa blocking, locking position over the head or other control structure ofthe screw, thereby automatically activating the blocking and lockingfeature of the bone treatment plate assembly to block withdrawal of thebone screw, and thus to lock the bone screw in the assembly and retainjoinder of the bone screw to the respective bone of the recipientuser/patient. Such bone screw can, of course, be released for removal bymanually or otherwise intentionally moving or flexing the band away fromthe screw, and removing the screw while the band is thus held in themoved or flexed condition.

In preferred embodiments of the invention, all of apertures 22 areslot-shaped in that, e.g. in projection, each aperture has an elongatedimension and a shorter cross-dimension. In some embodiments, two of theapertures are relatively lesser lengths, optionally circular, and serveas support apertures, and the remaining apertures are relatively greaterlengths, as slots or slot-shaped, and serve as settle apertures,providing for the bone structure to settle while being advantageouslyheld by the bone treatment plate. In still other embodiments, all ofapertures 22 are circular. As seen in FIGS. 1 and 2, typically eachaperture along the length of the bone treatment plate assembly can beprogressively longer/shorter than the adjacent apertures in the samerow, to accommodate the progressively increasing distance moved byrespectively more upwardly-disposed ones of the vertebrae being treatedby the plate assembly. All of the slots have commonly oriented axesalong the elongate dimensions of the slots. Preferably, all apertures 22are slot apertures having relatively longer lengths and relativelyshorter widths.

Typical length increments for adjacent apertures are about 1 mm.Accordingly, in a plate 12 as in FIGS. 1-4 having 6 apertures per row,the length differential between the longest and shortest apertures 22can be, for example, about 5 mm. The exact and actual lengthdifferentials can be somewhat different, depending on the specific usecontemplated for the respective plate 12.

In an embodiment not shown, all of the bone screw apertures 22 arecircular. Accordingly, such assembly provides for fixed positioning ofthe bone being supported. Otherwise, all features of the spinal plateassembly are substantially the same as the elements and features of theassemblies of e.g. FIGS. 1-13. Thus, bands 36 and springs 38 all employthe same principles illustrated hereinabove.

Typically, spinal plate assemblies of the invention have two rows ofapertures 22. And while the spinal plate assemblies illustrated in thedrawings show 2 rows of bone screw apertures, the invention can well beutilized with any desired number of rows of apertures, and any desirednumber of apertures per row, or any other arrangements of aperture arraywhich enable desired post-procedural movement of the vertebrae withoutadding substantial bone-to-plate stress as a result of such relativemovement.

Those skilled in the art will now see that certain modifications can bemade to the apparatus and methods herein disclosed with respect to theillustrated embodiments, without departing from the spirit of theinstant invention. And while the invention has been described above withrespect to the preferred embodiments, it will be understood that theinvention is adapted to numerous rearrangements, modifications, andalterations, and all such arrangements, modifications, and alterationsare intended to be within the scope of the appended claims.

To the extent the following claims use means plus function language, itis not meant to include there, or in the instant specification, anythingnot structurally equivalent to what is shown in the embodimentsdisclosed in the specification.

1. A bone repair system, comprising: (a) a bone plate; and (b) a bonescrew retention mechanism comprising a spring structure (14) havingfirst and second ends, a length, a structure top and a structure bottom,and a structure height (H) therebetween, said spring structurecomprising (i) first and second resilient bands (36A, 36B) each havingfirst and second ends, a band top associated with the structure top, anda band bottom associated with the structure bottom, said resilient bandshaving respective lengths thereof, said first and second bands eachhaving an outer surface (46) facing outwardly of said spring structure,and an inner surface, the inner surfaces facing each other and facinginwardly into said spring structure, said first and second resilientbands defining a width (W1) of said spring structure between the outersurfaces (46); and (ii) resilient springs (38) spaced along the lengthof said spring structure, said resilient springs extending between andconnected to said resilient bands, and having spring lengths extendingbetween the first and second resilient bands, said resilient springshaving spring tops and spring bottoms, opposing spring sides, springheights between the spring tops and the spring bottoms, spring widths(W) between the opposing spring sides, angles α being defined betweenthe resilient springs (38) and the inner surfaces of said bands (36),and angles β being defined between the band tops and the spring tops,ratio W/H of the widths of the resilient springs (38) to the heights ofthe springs being less than 1/1, and wherein, when a squeezing force isapplied at a said end of said spring structure (14), which movesrespective ends of said first and second bands (36) resiliently towardeach other, said spring structure resiliently deflects so as toaccommodate reduced width (W1) of said spring structure (14) inpreference to deflecting in a direction corresponding to height (H),such that the response of said spring structure (14) to such squeezingforce is a preferential resilient change in magnitude of angle αrelative to change in magnitude of angle β: 2-7. (canceled)
 8. A bonerepair system as in claim 1 wherein said springs are arranged in groupsof at least three springs along said bands.
 9. (canceled)
 10. A bonerepair system as in claim 1 wherein the compositions of said bands areselected from the group consisting of titanium, titanium alloy, andstainless steel.
 11. A bone repair system as in claim 1 wherein saidsprings comprise substantially straight line compression springs.
 12. Abone repair system as in claim 1, said springs comprising at least threegroups of springs wherein each group comprises at least two springs, andwherein spacing between the springs in a group is less than spacingbetween the groups.
 13. A bone repair system as in claim 1 wherein saidfirst band (36A) has a first width (W3) and wherein said second band(36B) has a second width (W3) greater than the first width.
 14. A bonerepair system as in claim 1 wherein said spring structure comprisesplastic composition which is safe for use in living human or animalbodies, as an implantable plastic, and wherein said spring structure hassuitable strength, rigidity, and deflection properties to block screwwithdrawal in a routine implant use environment. 15-18. (canceled)
 19. Abone repair system as in claim 14 wherein the composition of said springstructure comprises at least one of titanium, titanium alloy, andstainless steel.
 20. A bone repair system as in claim 1 wherein thecompositions of said first and second bands comprise at least one oftitanium, titanium alloy, and stainless steel.
 21. A bone repair systemas in claim 1, at least one of said bands comprising amovement-arresting protuberance extending outwardly therefrom.
 22. Abone repair system as in claim 1, said bands comprising first and secondprotuberances extending from said bands and being effective, incombination with cooperating detents in a cooperating structure, andwherein said spring structure is otherwise confined with respect to suchother cooperating structure, to arrest longitudinal movement of saidspring structure along such other cooperating structure.
 23. A bonerepair system as in claim 1, said bands comprising first and secondprotuberances extending from said bands at or proximate the first endsof the bands, and third and fourth protuberances extending from saidbands at or proximate the second ends of the bands, said first, second,third, and fourth protuberances collectively being effective, incombination with a cooperating detent in another cooperating structure,and wherein said spring structure is otherwise confined with respect tosuch other cooperating structure, to arrest longitudinal movement ofsaid spring structure along such other cooperating structure. 24-97.(canceled)
 98. A bone repair system, comprising: (a) a bone plate; and(b) a bone screw retention mechanism comprising a unitary springstructure (14) having first and second ends, a length, a structure topand a structure bottom, and a structure height (H) therebetween, saidunitary spring structure comprising (i) first and second bands (36A,36B) each having first and second ends, a band top associated with thestructure top, and a band bottom associated with the structure bottom,said bands having respective lengths thereof, said first and secondbands each having an outer surface (46) facing outwardly of said springstructure, and an inner surface, the inner surfaces facing each otherand facing inwardly into said spring structure, said first and secondbands defining a width (W1) of said spring structure between the outersurfaces (46); and (ii) springs (38) spaced along the length of saidspring structure, each said spring extending from said first band tosaid second band, said springs having spring tops and spring bottoms,opposing spring sides, spring heights between the spring tops and thespring bottoms, spring widths (W) between the opposing spring sides,angles α being defined between the respective springs (38) and the innersurfaces of said bands (36), and angles β being defined between the bandtops and the spring tops, said first and second bands and said springsbeing fabricated from a single piece of material, ratio of the widths(W) of the springs to the heights of the springs being less than 1/1,and wherein, when a squeezing force is imposed on said spring structure(14), squeezing said first and second bands (36) toward each other, saidspring structure resiliently deflects so as to accommodate reduced width(W1) of said spring structure (14) in preference to deflecting in adirection corresponding to height (H), such that the response of saidspring structure (14) to such squeezing force is a preferentialresilient change in magnitude of angle α relative to change in magnitudeof angle β.
 99. A bone repair system as in claim 98 wherein the opposingspring sides, between the spring tops and the spring bottoms, are mirrorimages of each other.
 100. A bone repair system as in claim 1, saidsprings comprising at least six individual springs substantially equallyspaced from each other.
 101. A bone repair system as in claim 1 whereinthe opposing spring sides, between the spring tops and the springbottoms, are mirror images of each other.
 102. A bone repair system asin claim 10 wherein the opposing spring sides, between the spring topsand the spring bottoms, are generally parallel to each other.